Evaluations of man-made salt marshes in the Dutch Wadden Sea, on the northern coast of the Netherlands, found that they may be more economically viable than increasing the height of dikes and thus potentially reduce the need for dike reinforcement. 

Nature-based Intervention:

Classified as semi-natural habitats, approximately 9000 hectares of constructed salt marshes exist on the shores of the Netherlands and the barrier islands. For a particular case study location in the Netherlands where 25 kilometers of man-made salt marsh were constructed along a dike, a cost-effectiveness evaluation found salt marsh construction to be more cost-effective than dike heightening in instances where economic damage in the case of dike breaching is small to moderate. Models of the system showed that construction of earthen breakwaters within the saltmarsh, above the area where sediment naturally accumulates, appears to be more effective than increasing the height of the dike itself. The Wadden Region Delta Programme has therefore determined through its research that integrating salt marshes into flood defense plans in this region is a preferred strategy for climate change adaptation.

Overview of context and outcomes:

The Wadden Sea lies between the coasts of the Netherlands, Germany and Denmark and a string of barrier islands stretching 500 kilometers separating it from the North Sea. Consisting of tidal mudflats and salt marshes, it is an important biologically productive ecosystem, of which several stretches have earned the title of UNESCO World Heritage Sites.